Distribution of Cr3+ between octahedral and tetrahedral sites in synthetic blue and green (CaMgSi2O6)95(CaCrAlSiO6)5 diopsides

2019 ◽  
Vol 83 (4) ◽  
pp. 497-505
Author(s):  
Masahide Akasaka ◽  
Yohei Takasu ◽  
Makoto Handa ◽  
Mariko Nagashima ◽  
Maki Hamada ◽  
...  
Keyword(s):  
Spectroscopic Analysis ◽  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Rietveld Method ◽  
Tetrahedral Coordination ◽  
X Ray Diffraction ◽  
Coordination Polyhedra ◽  
X Ray ◽  
Tetrahedral Sites ◽  
Bluish Green

AbstractThe distribution of Cr3+ ions in blue and green diopsides crystallised from a glass with the composition [CaMgSi2O6 (Di)]95[CaCrAlSiO6 (CrAlTs)]5 (mol.%) was determined using Rietveld refinement of X-ray diffraction data in order to evaluate published results by optical spectroscopic analysis, and to clarify the influence of Cr3+–Al3+ distribution between the octahedral M1 and tetrahedral T sites on the crystal structure. The starting material was Di95CrAlTs5-diopside crystallised from glass at 800°C for 2 days. After another 19 days at 800°C and 1000°C for 7 days, the diopsides remained blue. The blue diopside gradually changed to bluish green by heating at 1200°C for 3 days and to green after 7 days. The stoichiometric compositions of the synthesised phases were confirmed by electron microprobe analysis. The Cr occupancies refined by the Rietveld method resulted in the site populations in the M1 and T sites: M1[Mg0.95Cr0.030(4)Al0.020]T[Si1.950Cr0.020Al0.030] and M1[Mg0.95Cr0.037(4)Al0.013]T[Si1.950Cr0.013Al0.037] (per 6 oxygens) for the blue diopsides at 800 and 1000°C, respectively: M1[Mg0.95Cr0.042(3)Al0.008]T[Si1.950Cr0.008Al0.042] for the bluish green diopside at 1200°C for 3 days; and M1[Mg0.95Cr0.049(3)Al0.001]T[Si1.950Cr0.001Al0.049] for the green diopside at 1200°C for 7 days. Such Cr and Al distributions effect the volumes and site distortions of the octahedral and tetrahedral coordination polyhedra: the TO4 tetrahedron volumes of the blue diopsides (2.251–2.258 Å3) are larger than that of the green diopside (2.237 Å3); the M1O6 octahedron volumes of the former (11.74–11.77 Å3) are smaller than that of the latter (11.86 Å3); the TO4 tetrahedra in the blue diopside (<λtet> =1.006; σθ(tet)2 = 24.37–24.69) are less distorted than that of the green diopside (<λtet> = 1.007; σθ(tet)2 = 27.94); the M1O6 octahedra in the former (<λoct> =1.006; σθ(oct)2 = 20.39–21.13) are more distorted than that of the latter (<λoct> = 1.005; σθ(oct)2 = 17.58).

Ardennite, tiragalloite and medaite: structural control of (As5+,V5+,Si4+)O4 tetrahedra in silicates

2010 ◽  
Vol 74 (1) ◽  
pp. 55-71 ◽  
Author(s):  
M. Nagashima ◽  
T. Armbruster
Keyword(s):  
Structural Control ◽  
Ionic Radius ◽  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Tetrahedral Coordination ◽  
X Ray Diffraction ◽  
X Ray ◽  
P Content ◽  
The Mean ◽  
Si Content

AbstractSeveral silicate-minerals, such as ardennite – Mn2+4MgAl5[Si5(As5+,V5+)O22](OH)6, Z = 2, tiragalloite – Mn2+4[Si3As5+O12(OH)], Z = 4 and medaite – Mn2+6[Si5(V5+,As5+)O18(OH)], Z = 4 possess (V5+,As5+,P5+)O4 tetrahedra. Using electron-microprobe analysis (EMPA) and single-crystal X-ray diffraction methods, the crystal chemistry of ardennite from Salam-Château, Belgium and the Vernetto mine, Italy, tiragalloite from the Gambatesa mine, Italy, and medaite from the Molinello mine, Italy and the Fianel mine, Switzerland, were studied. Structure refinements converged to R1 values of 2.10–5.67%. According to chemical analysis, the Σ(As+V+P) content increases with decreasing Si content. Thus, Si replaces pentavalent cations in tetrahedral coordination. The (As5+,V5+,P5+,Si4+)O4 tetrahedra are categorized by their connections to SiO4 tetrahedra. The (As5+,V5+,P5+,Si4+)O4 tetrahedron of ardennite is isolated, and those of tiragalloite and medaite terminate a tetrahedral chain. The <T–O> of the isolated (As5+,V5+,P5+,Si4+)O4 tetrahedron shows a positive correlation with the mean ionic radius. For (As5+,V5+,P5+,Si4+)O4 tetrahedra with one T–O–T link, <T–O> and mean ionic radius are also correlated. In addition, the longest bridging T–O bond occurs between (As,V,P,Si)O4 and the adjacent SiO4 tetrahedron. The bridging O atom is over-bonded to satisfy the charge requirement of Σ(As+V+Si).

The crystal structure of kiddcreekite solved using micro X-ray diffraction and the EPCryst program

2014 ◽  
Vol 78 (7) ◽  
pp. 1517-1525 ◽  
Author(s):  
Liu Wenyuan ◽  
Dong Cheng ◽  
Gu Xiangping ◽  
Liu Yu ◽  
Qiu Xiaoping ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Rietveld Method ◽  
Lattice Parameter ◽  
X Ray Diffraction ◽  
Single Crystal Diffraction ◽  
X Ray ◽  
Covellite Ore ◽  
Space Method

AbstractAbundant kiddcreekite grains were identified in the Zijinshan Cu-Au epithermal deposit in Fujian Province, China. The mineral occurs as polycrystalline grains, 5–300 μm in size, associated with colusite, enargite, stannoidite, mawsonite, vinciennite, hemusite, tennantite and wolframite in a predominantly covellite ore. Based on electron microprobe analysis, the empirical formula of the kiddcreekite is Cu6.2Sn0.97W0.95S7.83, without significant Se or Te contents. The crystal structure of kiddcreekite was solved using the direct-space method (EPCryst) from laboratory micro X-ray diffraction (μXRD) data and refined by the Rietveld method. The R values of the final Rietveld refinement were Rp = 9.06%, Rwp = 8.31%, RB = 3.16 and RF = 2.17%. Kiddcreekite has a cubic structure, space group F4̄3m and lattice parameter a = 10.8178(3) Å (Z = 4, V = 1265.95(6) Å3). In the unit cell, W, Sn and Cu atoms occupy the 4a, 4c and 24f Wyckoff positions, respectively, and S atoms occupy two sets of 16e Wyckoff positions. The structure of kiddcreekite consists of stacked double MeS4 layers (giving a W–Sn–Cu tier and a Cu–vacancy tier) as in the sphalerite substructure. This study also demonstrates the possibility of using laboratory µXRD data coupled with the direct-space method to solve inorganic structures in cases where samples are too small for conventional powder and single-crystal diffraction.

Crystal-chemical aspects of the roméite group, A2Sb2O6Y, of the pyrochlore supergroup

2017 ◽  
Vol 81 (6) ◽  
pp. 1287-1302
Author(s):  
Ferdinando Bosi ◽  
Andrew G. Christy ◽  
Ulf Hålenius
Keyword(s):  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Structural Parameters ◽  
Chemical Information ◽  
Crystal Chemical ◽  
X Ray Diffraction ◽  
Structural Variations ◽  
X Ray ◽  
End Members ◽  
Charge Balancing

AbstractFour specimens of the roméite-group minerals oxyplumboroméite and fluorcalcioroméite from the Långban Mn-Fe deposit in Central Sweden were structurally and chemically characterized by single-crystal X-ray diffraction, electron microprobe analysis and infrared spectroscopy. The data obtained and those on additional roméite samples from literature show that the main structural variations within the roméite group are related to variations in the content of Pb2+, which is incorporated into the roméite structure via the substitution Pb2+→A2+ where A2+ = Ca, Mn and Sr. Additionally, the cation occupancy at the six-fold coordinated B site, which is associated with the heterovalent substitution BFe3+ + Y☐→BSb5++YO2-, can strongly affect structural parameters.Chemical formulae of the roméite minerals group are discussed. According to crystal-chemical information, the species associated with the name ‘kenoplumboroméite’, hydroxycalcioroméite and fluorcalcioroméite most closely approximate end-member compositions Pb2(SbFe3+)O6☐, Ca2(Sb5+Ti) O6(OH) and (CaNa)Sb2O6F, respectively. However, in accord with pyrochlore nomenclature rules, their names correspond to multiple end-members and are best described by the general formulae: (Pb,#)2(Sb,#)2O6☐, (Ca,#)2(Sb,#)2O6(OH) and (Ca,#)Sb2(O,#)6F, where ‘#’ indicates an unspecified charge-balancing chemical substituent, including vacancies.

Synthesis, structure and thermal expansion of the phosphates M0.5+x M′x Zr2−x (PO4)3 (M, M′–metals in oxidation state +2)

2017 ◽  
Vol 89 (4) ◽  
pp. 523-533 ◽  
Author(s):  
Elena Asabina ◽  
Vladimir Pet’kov ◽  
Pavel Mayorov ◽  
Dmitriy Lavrenov ◽  
Igor Schelokov ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Thermal Treatment ◽  
Ir Spectroscopy ◽  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Sol Gel ◽  
X Ray Diffraction ◽  
X Ray ◽  
Structural Types ◽  
The Difference

AbstractThe phosphates M0.5+x M′x Zr2−x (PO4)3 (M–Ca, Mn, Co, Sr, Cd, Ba, Pb; M′–Mg, Mn, Co) were synthesized by sol-gel method with the following thermal treatment of reaction mixtures. X-ray diffraction, IR spectroscopy and electron microprobe analysis showed that the obtained phosphates crystallized in Sc2(WO4)3 (SW) and NaZr2(PO4)3 (NZP) structural types. Both types of crystal structures are based on a framework comprised of octahedra and tetrahedra, the difference between them is fragments orientation. Thermal expansion of the phosphates was studied in the temperature range 20–800°C. Some compounds were found to belong to low-expanding materials (αav ~2·10−6°C−1).

X-ray Intensities from Copper-Target Diffraction Tubes

1976 ◽  
Vol 20 ◽  
pp. 565-574
Author(s):  
M. A. Short
Keyword(s):  
Close Agreement ◽  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
X Ray Diffraction ◽  
Characteristic Radiation ◽  
Tube Voltage ◽  
X Ray ◽  
Copper Target ◽  
Fine Focus ◽  
Constant Potential

The relative intensities of the Kα characteristic radiation obtained from copper-target X-ray diffraction tubes have been calculated for a range of tube accelerating voltages and take-off angles. The calculations employ an over-voltage function, and absorption and atomic number corrections similar to those used in electron microprobe analysis. They apply only to constant potential X-ray generators. Measurements of actual intensities obtained on a Picker diffractometer using a sodium chloride monochromator gave relative intensities in close agreement with those calculated. The calculations and measurements show that there is an optimum tube voltage, with respect to intensity, for each take-off angle. This voltage increases with increasing take-off angle. The application of these results to the consideration of the relative intensities obtainable from broad, standard and fine focus copper-target X-ray diffraction tubes is discussed.

X-ray Diffraction/Electron Microprobe Analysis of Surface Films Formed on Alloys During Hydrothermal Reaction with Geologic Materials

1984 ◽  
Vol 28 ◽  
pp. 367-375 ◽  
Author(s):  
R. G. Johnston ◽  
M. B. Strope ◽  
R. P. Anantatmula
Keyword(s):  
Electron Microprobe ◽  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Hydrothermal Reaction ◽  
Pressure Vessels ◽  
Surface Films ◽  
X Ray Diffraction ◽  
X Ray ◽  
Geologic Materials ◽  
Structure Phase

AbstractX-ray diffraction and electron microprobe analysis were used in combination to identify reaction phases that formed on the surfaces of low-carbon steel specimens reacted with a 75% basalt-25% bentonite mixture and anion-doped water in sealed pressure vessels at 100°C and 250°C. Reaction phases on specimen surfaces and in adhering geologic material were identified by conventional X-ray diffraction scans of entire specimens with intact reaction layers. Comparison of results from adhering geologic material and scans of selectively removed layers allowed establishment of approximate reaction gradients in the adhering packing material. Electron microprobe analysis of specimens in cross-section provided quantitative chemical analyses of adhering reaction phases, and identification of reaction layer composition gradients and thicknesses. Magnetite formed on the surface of specimens reacted at 250°C for 4 weeks. Iron-enriched clay was also observed on specimen surfaces and in the adjacent basalt-bentonite mixture. The 100°C experiments yielded surface films of a siderite-structure phase, (Fe,Ca,Mn)CO3, that were not observed in previous experiments with synthetic ground-water. Less extensive iron enrichment of the adjacent clays compared to that seen in the 250°C experiments was observed. The siderite-structure phase generally formed when no carbonate ion was present in the initial solution, implying dissolution of impurity calcite in the bentonite as the controlling factor in the reaction. The results demonstrate the utility of combining X-ray diffraction and electron microprobe analysis for characterization of reaction phases on alloys reacted with complex geologic materials.

Synthesis of Ferroelectric Strontium Bismuth Tantalate Films from Metal Alkoxide Precursors

1996 ◽  
Vol 453 ◽  
Author(s):  
Wei-Wei Zhuang ◽  
Lumei Liu ◽  
Naijuan Wu ◽  
Zhidong Hao ◽  
David M. Hoffman ◽  
...  
Keyword(s):  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Metal Alkoxide ◽  
X Ray Diffraction ◽  
Strontium Bismuth Tantalate ◽  
X Ray ◽  
Force Microscopy ◽  
Atomic Force ◽  
Saturation Polarization ◽  
Alkoxide Precursors

AbstractFerroelectric SrBi2Ta2O9 (SBT) films were prepared by the spin coating technique on platinum, quartz and YBa2Cu3O7-x/LaA1O3 substrates from a methoxyethanol solution of bismuth isopropoxide (Bi(OCH(CH3)2)3) and strontium tantalum isopropoxide (SrTa2(OCH(CH3)2)12). X-Ray diffraction studies showed some crystallization occurred after annealing the films under oxygen flow at 600 °C and excellent crystallinity was achieved after annealing at 750 °C for 0.5 h. Electron microprobe analysis gave a composition close to that expected for SBT, and atomic force microscopy gave a root mean square surface roughness of 101 A. An hysteresis measurement (1 kHz) gave remnant polarization (2Pr), saturation polarization (Ps) and coercive field (Ec) values of 14.5 μC/cm2, 14.5 μ/cm2 and 59 kV/cm, respectively.

scholarly journals Crystallochemical aspects of two microlite-group new mineral species

2014 ◽  
Vol 70 (a1) ◽  
pp. C1095-C1095
Author(s):  
Marcelo Andrade ◽  
Javier Ellena ◽  
Daniel Atencio
Keyword(s):  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
New Mineral ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
New Mineral Species ◽  
Group 1

Fluorcalciomicrolite, Ca1.5Ta2O6F, and hydroxycalciomicrolite, Ca1.5Ta2O6(OH), are new microlite-group [1] minerals found in the Volta Grande pegmatite, Nazareno, Minas Gerais, Brazil. Both occur as octahedral and rhombododecahedral crystals. The crystals are colourless, yellow and translucent, with vitreous to resinous luster. The densities calculated for fluorcalciomicrolite [2] and hydroxycalciomicrolite are 6.160 and 6.176 g/cm3, respectively. The empirical formulae obtained from electron microprobe analysis are (Ca1.07Na0.81□0.12)Σ2(Ta1.84Nb0.14Sn0.02)Σ2[O5.93(OH)0.07]Σ6.00[F0.79(OH)0.21] for fluorcalciomicrolite and (Ca1.48Na0.06Mn0.01)Σ1.55(Ta1.88Nb0.11Sn0.01)Σ2O6[(OH)0.76F0.20O0.04] for hydroxycalmicrolite. Fluorcalciomicrolite is cubic, space group Fd-3m, a = 10.4191(6) Å, V = 1131.07(11) Å3, and Z = 8. Hydroxycalciomicrolite is also cubic; however, the presence of P-lattice is confirmed by the large number of weak reflections observed by X-ray diffraction. As a result, the space group is P4332 and unit-cell parameters are a = 10.4211(8) Å, and V = 1131.72(15) Å3.

Monoclinic structure and nonstoichiometry of `KAlSiO4-O1'

2013 ◽  
Vol 69 (4) ◽  
pp. 334-336 ◽  
Author(s):  
Aleksandar Kremenović ◽  
Biljana Lazic ◽  
Hannes Krüger ◽  
Martina Tribus ◽  
Predrag Vulić
Keyword(s):  
Single Crystal ◽  
Electron Microprobe ◽  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Monoclinic Structure ◽  
X Ray Diffraction ◽  
Flux Method ◽  
X Ray ◽  
Derivatives Of ◽  
Aluminium Silicate

Crystals of KAlSiO4-O1(potassium aluminium silicate) were synthesized using a flux method and analysed utilizing single-crystal X-ray diffraction and electron microprobe analysis. Both methods confirm that the crystals are nonstoichiometric according to K1−xAl1−xSi1+xO4withx= 0.04 (1). KAlSiO4-O1is closely related to the stuffed derivatives of tridymite, although the topology of the Si/Al-ordered framework is different. Six-membered rings of UUDDUD and UUUDDD (U = up and D = down; ratio 2:1) configurations are present in layers parallel to theabplane. In contrast, the framework of tridymite exhibits UDUDUD rings. The crystals are affected by inversion, pseudo-orthorhombic and pseudo-hexagonal twinning.

Clino-suenoite, a newly approved magnesium-iron-manganese amphibole from Valmalenco, Sondrio, Italy

2018 ◽  
Vol 82 (1) ◽  
pp. 189-198
Author(s):  
Roberta Oberti ◽  
Massimo Boiocchi ◽  
Frank C. Hawthorne ◽  
Marco E. Ciriotti ◽  
Olav Revheim ◽  
...  
Keyword(s):  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Structure Refinement ◽  
Type Specimen ◽  
Crystal Structure Refinement ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Iron Manganese

ABSTRACTClino-suenoite, ideally □${\rm Mn}_{2}^{2 +} $Mg5Si8O22(OH)2 is a new amphibole of the magnesium-iron-manganese subgroup of the amphibole supergroup. The type specimen was found at the Lower Scerscen Glacier, Valmalenco, Sondrio, Italy, where it occurs in Mn-rich quartzite erratics containing braunite, rhodonite, spessartine, carbonates and various accessory minerals. The empirical formula derived from electron microprobe analysis and single-crystal structure refinement is: ANa0.04B(${\rm Mn}_{1.58}^{2 +} $Ca0.26Na0.16)Σ2.00C(Mg4.21${\rm Mn}_{0. 61}^{2 +} {\rm Fe}_{0.04}^{2 +} $Zn0.01Ni0.01${\rm Fe}_{0.08}^{3 +} $Al0.04)Σ5.00TSi8.00O22W[(OH1.94F0.06)]Σ=2.00. Clino-suenoite is biaxial (+), with α = 1.632(2), β = 1.644(2), γ = 1.664(2) and 2Vmeas. = 78(2)° and 2Vcalc. = 76.3°. The unit-cell parameters in the C2/m space group are a = 9.6128(11), b = 18.073(2), c = 5.3073(6) Å, β = 102.825(2)° and V = 899.1(2) Å3 with Z = 2. The strongest ten reflections in the powder X-ray diffraction pattern [d (in Å), I, (hkl)] are: 2.728, 100, (151); 2.513, 77, ($\bar 2$02); 3.079, 62, (310); 8.321, 60, (110); 3.421, 54, (131); 2.603, 42, (061); 2.175, 42, (261); 3.253, 41, (240); 2.969, 40, (221); 9.036, 40, (020).

Sign in / Sign up

Export Citation Format

Share Document